Be基蓝绿激光器载流子约束的LCAO理论研究

Carrier Confinement in Be-based Blue/Green Laser Diodes

本征的强离子性，使ZnSe基半导体蓝绿激光器易于形成堆垛层错等退化缺陷，严重地影响了器件的寿命。人们便开始将注意力投向离子性较低的Be基化合物，希望用Be基Ⅱ-Ⅵ族材料取代ZnSe基材料，抑制蓝绿激光器的退化。要研制半导体激光器，电学限制层对发光活性层中载流子的约束能力（即能带的offset值）是最重要的基本参数之一。由于对Be基化合物的了解十分有限，本文从基本的原子参数出发，用原子轨道线性组合（LCAO）理论计算了所有Ⅱ-Ⅵ族化合物价带顶的相对位置，结合带隙的实验值，给出了Ⅱ-Ⅵ族化合物导带底的相对位置。简要分析了二元化合物用于BeTe中载流于约束的可能性。根据虚晶近似，用插值方法计算了与GaAs匹配的Be基四元合金相对与BeTe价带、导带的offset。对各四元合金的特征进行了分析对比，讨论了Be基四元合金用作我流子约束层的可能性。为制作Be基半导体蓝绿激光器提供了能带剪裁的理论依据。

Because of the intrinsically high ionicity the degradation defects 5 such as stacking faults, are easily formed in ZnSe based Ⅱ-Ⅳ materials, and have been hindering us foryears from fabricating practical blue/green laser diodes with long lifetime. To circumvntthis problem, people have been paying their attention to Be-based compounds of relatively low ionicity, in an attempt to restrain the degradation defects in laser diodes byreplacing ZnSe based materials with Be-based materials- Since the carrier confinement,described by the quantity of band offSet between the electrical coallnement layer and theactive layer, is undoubtedly one of the most important and most basic parameters to asemiconductor laser diode, we will give out in this paper the band offiet8 between theGaAs-matChed Be-based quaternaries(as electrical confinement loprs) and BeTe(as activelayer). Because the knowledge of Be-based compounds is rather limited, it is necessaryto carry out a systematically theoretical study on their energy gaps and lattices to searchout some new appropriate materials for blue/green light emitting devices. Based on thebasic parameters of the component at0ms, the valence band offsets of all EN compoundsincluding Be-VIs have been calculated in a LCAO (linear combination of atomic orbitals)scheme. The conduction band offsets have als0 been given out with the adoption of the ex-perimental values of energy gap. According to tlie above results of band offiet, we analyzebriefly the possibilities of using llN binaries as carrier (electron and hole) coallnementlayers to BeTe active layer. Mainly, the covalence band offsets and conduction band offsets, reIative to BeTe, of Be-based quaternaries lattice matched to GaAs substrate liavebeen caIculated by an interpolation under the pseudocrystaI approximation. Comparingand contrasting the theoretical results of all the quaternaries, we discuss the possibilitiesof Be based quaternaries adopted as carrier coallnement layers to BeTe active layer. In aword, we provide here s0me valuable theoretical bases of a energy band tailoring,, forBe-based blue/green laser diodes。